Bisphenols are used for the preparation of a variety of useful polymeric materials, including epoxy resins, polyesters, polycarbonates, and especially polyarylethers as described in, for example, U.S. Pat. No. 4,175,175. However, the ketal bisphenols of this invention are novel compounds.
The formation of the ketal moiety in a number of diverse organic compounds is well known in the art. The processes for the preparation of ketals and their corresponding heteroatom analogues, such as hemithioketals, can be accomplished by a number of synthetic methods. Examples of such methods have been reviewed, for example, in the following: H. J. Lowenthal in "Protective Groups in Organic Chemistry," J. F. W McOmie, ed., Plenum Press, 1973, p. 323ff; S. R. Sandler et al., "Organic Functional Group Preparations," Vol. 3, Academic Press, 1972, p. 2ff; C. A. Buehler et al., "Survey of Organic Synthesis," Wiley-Interscience, 1970, p. 513ff and vol. 2, 1977, p. 461ff; R. T. Bergstrom in "The Chemistry of Ethers, Crown Ethers, Hydroxyl Groups and Their Sulfur Analogues," Suppl. E, Part 2, S. Patai, ed., Wiley, 1980, p. 881ff; and F. A. J. Meskens, Synthesis, 501(1981).
Commonly, the ketal group is formed by reacting the corresponding carbonyl group with an alcohol or an alcohol derivative such as an orthoester, generally in the presence of an acid catalyst. It is also advantageous to conduct the reaction under conditions so as to remove the water of reaction and by-products, as for example, by distillation, by employing azeotropic solvents, as described in, for example M. Sulzbacher et al, J. Amer. Chem. Soc., 70, 2827 (1948), by using drying agents, or by adding chemical agents such as trialkyl orthoesters or tetraalkyl orthosilicates.
The use of clay catalysts to prepare ketals is known in the art as taught by Thuy et al., (Bull Soc. Chim. France, 2558 (1975)) and by Taylor et al., (Synthesis, 467 (1977)) both of which employed montmorillonite clay catalysts. However in the case of the heretofore unknown ketal bisphenol monomers of this invention, improved processes for the efficient preparation of said monomers are highly desirable.
U.S. Pat. No. 3,734,888 is directed to polyketals and a process for their preparation. The polyketals are described in this patent as containing groups of the formula: ##STR1## wherein the R is hydrogen or alkyl of 1 to 3 carbon atoms and n is 2 or 3. The polyketals are prepared by reacting an aromatic polyketone and a diol of the formula HO--(CR.sub.2).sub.n --OH in the presence of an acid catalyst. The polyketals in the reference are described as soluble in solvents, and solutions of the polyketals in such solvents are useful as coating lacquers for metal conductors in wire or sheet form, for various plastic films, such as polyamides and polyesters and as adhesives. Additionally, the polyketals are described as useful in film or powder form as adhesives in thermally bonding metals and plastics when melt pressed to such materials.